Don't know about the 2 1/4 oz. Gibbs Polaris but the 3 1/2 oz. version has no sinking problems that I've noticed.
At least the ones I'm using, which may be a year old, seem to be fine. If you have to retrieve the Polaris fast to keep it on top - you lose it's attractiveness.
What about the local fellow with the Hawg Hunter - that could be an option.